The present invention relates to a method of combating certain pathogenic agents in the environment, such as insects and parasites, and in particular certain living creatures that give rise to allergies, specifically acarids or xe2x80x9cmitesxe2x80x9d.
The prior art which is described more specifically below is intended for combating acarids, but it should be understood that this description is in general transposable to most methods of combating most insects and parasites in the environment.
Products derived from pyrethrum such as pyrethrinoids are known to constitute substances that are highly toxic for cold-blooded creatures, such as insects and parasites, whereas they are less toxic for man and other warm-blooded creatures.
Compositions are known comprising a compound of the pyrethrinoid family in a solvent, with the pyrethrinoid commonly used being permethrin whose formula is C21H20Cl2O3; these compositions are generally activated (also said to be xe2x80x9csynergizedxe2x80x9d) by means of an activator (or xe2x80x9csynergizerxe2x80x9d) such as piperonyl butoxide (PBO).
At present, numerous methods are used for combating acarids.
Thus, carpet cleaning shampoos and/or anti-acarid paints are used containing said compositions.
Studies have shown that when shampoos are applied, even with careful brushing, only some of the acarids are destroyed. Furthermore, those methods do not enable an entire room to be treated.
In addition to those treatments and in order to improve the destruction of acarids in a room, it is possible to diffuse compositions based on permethrin and PBO by means of a spray or an aerosol.
Although it is possible to use a spray or an aerosol to apply local treatment on surfaces soiled by acarids, under no circumstances is it possible for them to constitute means that are effective in eradicating all of the acarids present in a room.
Even under the optimistic assumption that a user has sprayed present compositions exhaustively over all surfaces, there nevertheless remains a non-negligible fraction of acarids that are not on the surface but that are inside certain items such as mattresses, carpets, . . . ; those acarids which cannot be destroyed by the above-described contact treatment operations will be able to develop and proliferate again.
At present, the most suitable treatment for combating acarids present in a residential room, both on its surfaces and within certain items such as mattresses, carpets, etc. . . . is to use a single-discharge aerosol.
That type of aerosol is calibrated as a function of the volume of the room to be treated and is designed to lower the population of acarids as much as possible in a single treatment.
Nevertheless, it suffers from the major drawback of being for a single use only. After being opened, such cans diffuse their composition that is active against acarids, i.e. an acaricidal composition, until they are completely empty.
Thus, in order to achieve effective treatment for a home, for example, it is necessary to purchase as many single-discharge aerosols as there are rooms in the home, and even then there remains the question of treating the common portions.
Such single-discharge aerosols also present the major drawback of preventing access to the room under treatment for several hours after the treatment operations have terminated because of the aggressive and irritant or even toxic nature of the active substance present in the concentrations that are obtained in the atmosphere of such a room.
Furthermore, all of the methods described above for using acaricidal compositions require compositions to be used whose concentration in permethrin, an active substance that is relatively expensive, lies in the range 1% to 3% by weight.
Furthermore, it is common practice to activate permethrin by using three times its weight of PBO, thereby increasing the cost of manufacturing such compositions, and thus the cost of the associated diffusion devices.
In addition, known methods are methods that act by the active substances in the liquid state coming into direct contact, either immediately when applying a shampoo or else after a greater or lesser delay when using a spray or an aerosol, and regardless of whether or not it is a single-discharge spray or aerosol. Those methods release either droplets of a size more or less fine that falls quickly onto surfaces, or else they release a mist constituted by finer droplets which remain longer in suspension, but nevertheless fall onto exposed surfaces within not more than a few hours.
The present invention seeks to mitigate all of the above-mentioned drawbacks and proposes a method of combating insects and parasites, and in particular acarids, the method comprising a step of diffusing an acaricidal composition comprising permethrin in a solvent.
According to the invention, the method is such that a composition comprising permethrin and tetramethrin in a solvent is diffused in a chamber to be treated, in such a manner that such solvent is entirely in the gaseous state.
Thus, the molecules with acaricidal action are distributed uniformly throughout the volume to be treated and they act on all zones that might contain colonies of acarids, penetrating into the smallest nooks and crannies.
The method is both simple to use and not very constraining. In particular, the user can come and go in the room and make free use of its furniture, even simultaneously with treatment operations taking place.
Furthermore, the acaricidal composition associated with the method of diffusion is genuinely effective by enabling volumes and their content to be thoroughly treated by acaricidal compositions having a concentration by weight of active substances well below the concentrations of present compositions.
This effectiveness applies not only to curative treatment of volumes, i.e. destroying colonies of acarids that are already prior art, but also to preventative treatment of such volumes, serving both to limit normal development of acarids up to the reproductive adult stage and to destroy any acarids that may be reintroduced into the treated volume from the outside (external recontamination).
The present invention thus presents the two advantages of using little active substance and of diffusing an acaricidal composition that presents no danger for the health of the user, by a surprising synergistic effect between the acaricidal composition and the method of diffusing it.
The saving achieved because of the small quantities of active substance used is further improved by the method acting relatively quickly.
In an advantageous version of the invention, about 0.05% to 0.5% (by weight) of permethrin is used together with about 0.05% to 0.5% (by weight) of tetramethrin.
In an advantageous version, about 0.1% to 0.4% (by weight) of permethrin is used together with about 0.1% to 0.4% (by weight) of tetramethrin.
In a preferred version, substantially equal proportions of permethrin and of tetramethrin are used, preferably both equal to about 0.2% (by weight).
The quantities of the pyrethrinoids are well below those commonly used with known diffusion methods.
The method of the invention gives rise to far fewer secondary effects for the user and presents a toxic effect that is well below that of known methods.
In a preferred implementation of the invention, the total proportion of permethrin plus tetramethrin used is about 0.15% to 0.8% (by weight), and preferably about 0.2% to 0.6% (by weight).
The total quantity of pyrethrinoids used in the context of the present invention is well below that of the prior art, and genuine effectiveness can be achieved at concentrations by weight that are reduced to one-fifth.
Advantageously, said composition is diffused by means of a catalytic combustion burner, the solvent being the fuel, and being constituted by isopropyl alcohol, for example.
The invention also provides the use of a catalytic combustion flask for implementing the method of the invention for combating insects and parasites, and in particular acarids, the flask being suitable for containing a combustible composition and to receive, on a collar fixed to its neck, a catalytic combustion burner, said burner having a substantially axial cavity that is downwardly open and that receives a wick dipping into said composition, said burner optionally having a substantially axial annular groove extending from the top surface of the burner and separating the annular peripheral zone carrying the catalyst from the central zone that is catalyst-free and forms a vaporization zone, the cavity being formed in a mass of ceramic material that is free from catalyst, and/or a channel for putting the top portion of the cavity that receives the wick into communication with the atmosphere.